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View Full Version : Lathe language, what my mentor taught me..



Bill in Ky
12-27-2006, 10:38 AM
Correct me if I and my mentor are wrong. He taught me that the live center on a lathe was the one that was in the spindle, live meaning "rotated" center. The dead center was the one in the tailstock, it was dead as in needing lube, not rotated or a "ball bearing" center.
Has the language changed? What were you gentlemen taught?

Evan
12-27-2006, 10:41 AM
The business end of a live center rotates with the work. You decide.

A.K. Boomer
12-27-2006, 10:57 AM
Sounds Like its an old school expression, back in the day there were only "dead centers" they had no bearings and all required lube so it makes sense to call the drive part of the lathe "live center"
I think where the confusion started is when the bearing ends came to be on the dead centers, then people started calling the dead center a live center - maybe in an effort to seperate the two different means of holding long stock,
this is just my theory and as everybody knows i dont own a lathe:o

JCHannum
12-27-2006, 11:04 AM
Correct me if I and my mentor are wrong. He taught me that the live center on a lathe was the one that was in the spindle, live meaning "rotated" center. The dead center was the one in the tailstock, it was dead as in needing lube, not rotated or a "ball bearing" center.
Has the language changed? What were you gentlemen taught?

That is correct, centers are properly called solid centers or ball bearing centers as opposed to dead or live centers.

The solid "live center" for use in the headstock should be unhardened, to permit dressing when installed to ensure it is true to the spindle. The tailstock solid "dead center" is hard for best wearing properties.

What is now commonly referred to as a live center is more properly called a ball bearing center.

Usage has gotten away from that, and any solid center is usually referred to as a dead center, and ball bearing centers are referred to as live centers.

miker
12-27-2006, 05:35 PM
The terminology has changed. I have old books that refer to the pointy lump of metal rotated at the spindle as a Live Center and the pointy lump of metal held in the Tailstock as a Dead center.
I think of the centers as sitting on the bench side by side. One is just a pointy lump of metal (Dead center) and the other one is full of ball/needle rollers able to rotate (Live Center). That is usually how they are sold now. eg. http://www.hareandforbes.com.au/sample_2/home.php

Rgds

Evan
12-27-2006, 05:41 PM
The point is that a live center rotates with the work. It doesn't matter what end of the lathe it is on.

Frank Ford
12-27-2006, 07:07 PM
Do metal working guys ever refer to the headstock spindle center as a "drive center" the way woodworkers do?

Cheers,

Frank Ford
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Evan
12-27-2006, 07:11 PM
Drive centers exist but they aren't commonly used.

Ed Tipton
12-30-2006, 10:34 PM
Evan's got it right. Any center which rotates with the work, regardless of whether it is in the headstock or the tailstock end of the work, can be considered as a "live" center. The "dead" center by way of comparison does not rotate with the work and thus develops an element of friction as the workpiece rotates against it.
In today's shop, common shop language refers to a ball bearing center as a "live" center as a means of differentiating it from a center which has no bearing, but I don't believe that anyone who is a working machinist would argue if you referred to a "driven" center as a live center. It is a matter of context.
In one context, the terms "live" or "dead" refers to the actual physical characteristic of the center itself, without reference as to how the center is to be used. In the other context, the same terms are used as a way of defining how the center is being used in the actual application.
A lot of older machinists , (older meaning those who were learning their trade in a time or place where ball bearing centers were not commonplace), learned to think of centers in the context of how they were used in application, and thus spoke of them as being either "live" or "dead".
In today's shop, both are correct, depending on the context being used,:) but as previously stated, in today's world a "live" center usually means a ball bearing center.